Skill: Understand area as covering

Area tells how much surface is inside a shape. To find area, cover the shape with equal-sized squares that fit together with no gaps and no overlaps. Then count the squares.

Suppose this rectangle is covered with square units:

1. Count the squares in each row. There are $4$ squares in a row.
2. Count the rows. There are $3$ rows.
3. Count all the squares:
   $(4+4+4=12)$.

So, the area of the rectangle is

$$\boxed{12\text{ square units}}.$$

The word square is important because we measured the inside using square units. Area is not the same as perimeter: area measures the space inside, while perimeter measures the distance around the outside.